This invention relates to a cylinder-disabling control system for a multi-cylinder engine, especially that of a two-cycle engine, and more particularly to that allowing for continuous and smooth transition between the cylinder-disabling mode and the all-cylinders-engaged mode. This invention also relates to a method therefor.
Engines, especially two-cycle engines, have drawbacks in that scavenging exhaust gas is not efficient when driving at a low speed or with a low load, whereby exhaust gas is not fully expelled, and irregular combustion is likely to occur, leading to unstable engine revolutions.
A method is available for improving unstable engine revolutions. That is, a cylinder-disabling mode, in which at least one but not all of the cylinders are disabled so as to reduce the number of operating cylinders, is employed. By reducing the number of operating cylinders, it is possible to obtain the effects in that exhaust gas pressure (back pressure) in an exhaust system is reduced, and exhaust interference interfering with discharging exhaust gas and introduction of a scavenging stream is inhibited due to transmission of exhaust pulses, leading to an increase in intake volume per cylinder, thereby stabilizing the engine revolutions.
However, particularly for a multi-cylinder engine provided with an exhaust manifold to which each exhaust port is connected, simple disabling-cylinder operation is not sufficient for stabilizing low rpm-driving, and thus, selection of cylinders to be resumed, injection gas volume when resumed, and timing control of ignition must be conducted by taking into consideration the particular characteristics of the multi-cylinder engine with an exhaust manifold.